Mr. J. Walter Christie's major contributions to the Ordnance Corps were the combat vehicle concepts he designed. He developed a four-wheel-drive truck for General Pershing and his staff in 1916.
During World War I, he built the forerunners of modern self-propelled artillery, mounting 75mm, 3-inch, and 5-inch guns on four-wheel-drive chassis.
He built the first “convertible” vehicle, using tracks for cross-country mobility and rubber tires for high-speed travel on roads.
After the end of World War I, he continued his work on the design and prototyping of advanced combat vehicles, demonstrating the first amphibious tank, which swam across the Hudson River in 1923.
Although the U. S. Army never adopted any of Mr. Christie's designs as standard, it did buy several of his prototypes and the rights to their design. As a result, many of his design features, such as his trailing arm road-wheel suspension system, large road-wheel excursion, and high power-to-weight ratio have been incorporated into several subsequent generations of U. S. tanks.